Gas compressors exist in various forms and can have separated drive and compressor coupled by a drive shaft. Some related examples include, integrated hydroelectric generators, wind turbines with hub generators, etc. For pressurized devices such as compressors, several seals can be used to seal the shaft and various compressor stages from each other and from the atmosphere. Magnetic bearings may support moving machinery without physical contact. For example, they can levitate a rotating shaft, providing for rotation with very low friction and no mechanical wear. However in order to provide compression of a working fluid (e.g., air or other gaseous compounds) multiple seals may be needed between compressor stages and between the compressor and the atmosphere. Such seals can be low friction mechanical seals with a tortuous path from inlet to outlet to prevent leakages. An example of such a tortuous mechanical seal is a labyrinth seal.
A labyrinth seal may be comprised of many grooves that press tightly inside another axle, or inside a hole, so that the working fluid has to pass through a long and difficult path to escape. The grooves interlock, to produce the long characteristic path which slows leakage. For labyrinth seals on a rotating shaft such as in a gas compressor, a very small clearance must exist between the tips of the labyrinth threads, or labyrinth teeth, and the running surface of the labyrinth seal.
Labyrinth seals on rotating shafts provide non-contact sealing action by controlling the passage of fluid through a variety of chambers by centrifugal motion, as well as by the formation of controlled fluid vortices. At higher speeds, centrifugal motion forces the liquid towards the outside and therefore away from any passages. Similarly, if the labyrinth chambers are correctly designed, any working fluid that has escaped the main chamber becomes entrapped in a labyrinth chamber, where it is forced into a vortex-like motion. This acts to prevent its escape, and also acts to repel any other fluid.
As the rotational speed or RPM (revolutions per minute) increase, the gas compressor can impart a rotational or circumferential velocity on the compressed fluid, on the high-pressure side (or high pressure end) of the compressor stage. If left uncontrolled, the circumferential velocity of the compressed fluid can continue to increase upstream of the labyrinth seals, leading to vibrations, or self-excitation. The self-excitation can occur at a natural or resonant frequency, and can cause significant damage to compressor or motor components. In some examples, a controller can monitor vibrations and other parameters. The controller can further shut the compressor down in the event one or more parameters exceeds a predetermined limit. In some examples, swirl brakes can be used to reduce the circumferential velocity, or swirl, of the compressed fluid. The number and arrangement of the swirl brakes can maximize swirl reduction and enhance the performance of the compressor. The present disclosure is directed toward overcoming one or more of the problems discovered by the inventors or that is known in the art.